1. Field of the Invention
The present invention relates to an accumulator which is used as a pressure accumulator or a pulsation pressure damping device. The accumulator according to the present invention is used, for example, in a hydraulic system for a motor vehicle or a hydraulic system for an industrial equipment.
2. Description of the Conventional Art
Conventionally, as shown in FIG. 6, there has been known an accumulator 51 structured such that an accumulator housing 52 is provided with an oil port 53 which is connected to a pressure piping (not shown) of equipment, an internal portion of the accumulator housing 52 is sectioned into a gas chamber 56 filling the gas, and a fluid chamber 57 communicating with the oil port 53, by a bellows 54 and a bellows cap 55, and the accumulator 51 is activated to accumulate pressure and damp pulsation pressure on the basis of movement of the bellows cap 55, and extension and contraction of the bellows 54 so that gas pressure and liquid pressure balance (Japanese Unexamined Patent Publication No. 2005-098391).
Further, the accumulator 51 is provided with a safety mechanism 61 which prevents the bellows 54 from being damaged due to the unbalance between the gas pressure and the liquid pressure in the case that the pressure of the fluid chamber 57 is decreased together with the pressure decrease of the pressure piping. In other words, in the case that the pressure of the pressure piping is extremely decreased due to the operation stop of the equipment, the liquid (oil) within the fluid chamber 57 is discharged little by little from the oil port 53, the bellows 54 is expanded little by little by the filled gas pressure according to the liquid discharge, and the bellows cap 55 comes into contact with a seal 62 which is installed in the inner surface of the housing 52 so as to form a so-called zero-down state. In the zero-down state, the fluid chamber 57 is occluded by the seal 62 (a spatial position closer to an outer peripheral side than the seal 62 among the fluid chamber 57 is occluded), a part of the liquid is trapped within the fluid chamber 57, and the pressure of the trapped liquid and the gas pressure of the gas chamber 56 are balanced. Therefore, the bellows 54 is inhibited from being damaged due to an excess stress applied to the bellows 54.
However, in the prior art mentioned above, there is a case that a lip 62a of the seal 62 is inverted and is pinched between the seal retaining portion 63 and the bellows cap 55 as shown in FIG. 7B, in place of the case that the seal 62 comes into contact with the bellows cap 55 in a normal attitude as shown in FIG. 7A. There is a case that the seal 62 is damaged for the reason of the pinching, and the safety mechanism 61 is not activated so as to make the bellows 54 be damaged.